How to Stop Pumpkin Squash and Zucchini From Mildew

Question

I desperately need help! I have three large wooden apple boxes that are my veggie garden. They were filled with the recommended layers of sugar cane mulch, chicken manure and compost. The compost I used was mushroom compost from my local garden supplies.

I think THAT was the problem. I have pumpkins, zucchini and baby squash growing in them. For a long time the plants grew really big and well, and I got a heap of veggies on all plants. Then they started to develop powdery mildew. No matter how many times I treated them with mildew sprays (following the directions), they would recover briefly and then get sick again. Now the pumpkins have pretty much died, and the squash are really sick, some have died and many of the leaves are turning brown and crispy despite watering and liquid fertiliser.

I believe the soil is infected with the mould/mildew spores and that I am fighting a losing battle. I’m after some advice on what to do. Do I need to remove all the compost and replace it with a better (mould-free) one – this will be a massive job – or am I likely to get the same problem even without a mushroom compost? Can I save the plants I have, and if so, how? Any advice would be great.

Answer 1

The soil would not be the problem. The problem is likely the conditions around the plant. powdery mildew flourishes in damp environments. Plants in containers are often watered from above and grow in close quarters, which creates the ideal environment for this disease.

If possible, dry to water from below the leaves. If this is not possible, water only in the morning so that the sun has a chance to dry the leaves off for you. Also, set a fan pointing at the plants. An oscillating fan is best. This will improve the airflow around the plants and help keep the powdery mildew from forming.